I'm afraid I can't make a screengrab right now, but I've never seen this mentioned:

In ESB when the probe droid blows up, there's a quick shot, perhaps 4 frames, just before the explosion, that has a vertical scratch through the frame. It starts and stops with the edits on either side of the shot. Why a dupe of a scratched positive ended up in this, I have no idea, as ASAIK there aren't even any opticals in the shot.

Anyway, for Blu-Ray the scratch was finally fixed. IIRC it was still there in 2004.